Inherently light- and heat-stabilized polyamides

ABSTRACT

A process for preparing inherently light- and heat-stabilized polyamides comprises polymerizing in the presence of at least one triacetonediamine compound of the formula                    
     where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms, preferably alkyl having from 1 to 18 carbon atoms, or benzyl.

This is a Continuation Application of application Ser. No. 08/722,048,filed on Dec. 31, 1996, which is a National Stage application under 35U.S.C. 371, based on International Application No. PCT/EP 95/01,349,filed Apr. 12, 1995.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improved polyamides. More particularly,the present invention relates to inherently light- and heat-stabilizedpolyamides. The present invention further relates to a process forpreparing these polyamides and to their use.

2. Description of the Related Art

The heat stability of polyamides, including nylon 6 and nylon 66, isinsufficient for some applications. For instance, coloration problemscan arise as a result of chemical changes (oxidative/thermal damage) tothe polymer during carpet yarn or textile fabric heat setting. Bothcontinuous filaments and staple fibers may be affected. It is known toadd stabilizers to the polyamide to improve these properties. Such anaddition can take place before, during or after the polymerization, forexample during the processing. The customary known stabilizers are mixedinto the polymer and are not bonded to the polymer chain. Duringprocessing or use they can migrate, evaporate or wash out of the polymermore or less readily, so that the effectiveness of the stabilizationdecreases in an undesirable manner and the surroundings (air, dyebath)may become contaminated.

DE-A-20 40 975, Sankyo Co. Ltd., describes the stabilization ofsynthetic polymers, including polyamides, with 4-aminopiperidinederivatives. Among the multiplicity of 4-aminopiperidine derivativesdisclosed therein is 4-amino-2,2,6,6-tetramethylpiperidine (ef. No. 32on page 8 of the document). However, this piperidine derivative isneither particularly singled out nor used in any Example. According tothis reference, the 4-aminopiperidine derivatives are mixed with theready-prepared polymer without becoming attached to the polymer chain.

DE-C-39 32 912, Sandoz, concerns polyamides containing radicals withsterically hindered amino groups, especially2,2,6,6-tetramethyl-4-piperidyl radicals, incorporated in the molecule.The number of radicals is from 5 to 200 per polyamide molecule onaverage. According to this reference, these polyamides are useful, interalia, for improving the dyeability of polyamides and as lightstabilizers for plastics; they are to be incorporated in amounts of1-10% by weight, particularly in the melt.

A paper in Poly. Deg. and Stab. 21, 251-262 (1988), states that thelight stability of nylon 66 is improved on addition of2,2,6,6-tetramethyl-4-piperidinol (TMP). The authors assume (see p. 259)that the TMP has reacted with the carboxyl end groups of the polyamideduring a melt postcondensation of the TMP-including nylon 66 at 275° C.under a water vapor atmosphere. But, they say, there are signs of(undesirable) crosslinking during the later stages of irradiation.

It is known to use amines or mono- and dicarboxylic acids as chainregulators in the polymerization of polyamides, and monocarboxylic acidsare very predominantly used for this purpose in practice.

It is an object of the present invention to provide inherently light-and heat-stabilized polyamides and processes for preparing them.

We have found that this object is achieved when a triacetonediaminecompound of the formula

where R is hydrogen (4-amino-2,2,6,6-tetramethylpiperidine) orhydrocarbyl having from 1 to 20 carbon atoms, preferably alkyl(4-amino-1-alkyl-2,2,6,6-tetramethylpiperidine) having from 1 to 18carbon atoms, or benzyl, is added before or in the course of thepolymerization of the polyamides.

SUMMARY OF THE INVENTION

The present invention accordingly provides a process for preparingpolyamides, which comprises effecting the polymerization of startingmonomers in the presence of at least one triacetonediamine compound ofthe formula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,preferably alkyl having from 1 to 18 carbon atoms, or benzyl. Preferredembodiments of the process of this invention are described in subclaims.The present invention further provides an inherently light- andheat-stabilized polyamide containing an amine radical of the formula

where R is as defined above, chemically bonded to the polymer chain.Preferred polyamides of this invention are defined in correspondingsubclaims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The triacetonediamine compound is added to the starting monomers or thepolymerizing reaction mixture and becomes bonded to the end of thepolymer chain through reaction of its primary amino group with thestarting monomers or with the carboxyl groups of the polyamide beingformed. The secondary amino group of the triacetonediamine compound doesnot react because of steric hindrance. Thus, the triacetonediaminecompound also acts as a chain regulator.

The chemical bonding of the triacetonediamine compound to the polymerchain of the polyamide results in inherently stabilized polyamides beingobtained. The process of this invention thus offers the advantage ofobviating the otherwise necessary separate step of mixing a stabilizerinto the polyamide. This eliminates problems or quality reductions ascan arise on incorporation of a stabilizer following surface applicationto the polyamide granules as a result of incompatibility, viscositydegradation, migration, vaporization or washoff of the stabilizer or atwofold stress as with compounding, for example. The use of thetriacetonediamine compound in the process of this invention protects thepolyamides against damage by the action of heat and thermal oxidation inprocessing and use.

The polymerization of the starting monomers in the presence of thetriacetonediamine compound is preferably carried out according tocustomary processes. For instance, the polymerization of caprolactam inthe presence of triacetonediamine (R=H) can be carried out for exampleaccording to the continuous processes described in DE 14 95 198 and DE25 58 480. The polymerization of 66 salt in the presence oftriacetonediamine can be carried out by the customary batchwise process(see: Polymerization Processes p. 424-467, especially p. 444-446,Interscience, New York, 1977) or by a continuous process, for example asdescribed in EP 129 196. In principle, the triacetonediamine compoundand the starting monomers can be introduced into the reactor separatelyor as a mixture. The triacetonediamine compound is preferably addedaccording to a predetermined amount/time program.

In a preferred embodiment of the process of this invention, the startingmonomers used for polymerization are caprolactam or at least onedicarboxylic acid A selected from adipic acid, sebacic acid andterephthalic acid and at least one diamine selected fromhexamethylenediamine and tetra-methylene-diamine, or dicarboxylicacid-diamine salts thereof. Caprolactam is particularly preferred.Dicarboxylic acid A is particularly preferably adipic acid orterephthalic acid. Given the appropriate choice of starting monomers,the polymerization will lead to the preferred polyamides nylon 6, nylon66, nylon 46 or nylon 610.

In a preferred embodiment, the triacetonediamine compound is added tothe starting monomers in an amount of from 0.03 to 0.8 mol %, preferablyfrom 0.06 to 0.4 mol %, based on 1 mol of carboxamide groups of thepolyamide. This statement of quantity relates for example to 1 mole ofcaprolactam when nylon 6 is to be prepared or to 0.5 mol of 66 salt whennylon 66 is to be prepared. It was found that amounts below 0.03 mol %do not ensure sufficient stabilization, whereas amounts above 0.8 mol %make it impossible to achieve the desired degree of polymerization owingto the regulating effect of the triacetonediamine compound.

In a preferred embodiment of this invention, the triacetonediaminecompound is combined with at least one customary chain regulator.Examples of suitable chain regulators are monocarboxylic acids such asacetic acid, propionic acid and benzoic acid. The chain regulatorcombination and the amounts used are selected inter alia according tothe amino end group content desired for the end product and according tothe desired melt stability. The amino end group content depends on thedyeability desired for the filaments or fibers. The melt stabilitydepends on the practical requirements of processing products, especiallyin relation to spinning.

The nylon 6 (polycaprolactam) prepared by the process of this invention,as well as the triacetonediamine compound, preferably containsdicarboxylic acids B as chain regulators. More particularly, such nylon6 products, as well as possessing the requisite melt stability, thedesired filament or fiber dyeability and good light and heat stability,also possess improved strength for the filaments obtained, especiallyfilaments produced by high-speed spinning at very high rates of speed.

The dicarboxylic acids B used as chain regulators in combination withthe triacetonediamine compound can be identical to or different from thedicarboxylic acids used as dicarboxylic acid A. They are preferablyselected from: C₄-C₁₀-alkanedicarboxylic acids, especially adipic acid,azelaic acid, sebacic acid and dodecanedioic acid;C₅-C₈-cycloalkanedicarboxylic acids, especiallycyclo-hexane-1,4-dicarboxylic acid; and also benzene- andnaphthalene-dicarboxylic acids, especially isophthalic acid,terephthalic acid and naphthalene-2,6-dicarboxylic acid. Thedicarboxylic acids B are preferably used in an amount of from 0.06 to0.6 mol %, preferably from 0.1 to 0.5 mol %, based on 1 mol ofcarboxamide groups of the polyamide.

In another preferred embodiment, the polymerization of the process ofthis invention is carried out in the presence of at least one pigment.Preferred pigments are titanium dioxide or inorganic or organic coloringcompounds. The pigments are preferably added in an amount of from 0 to 5parts by weight, especially from 0.02 to 2 parts by weight, based on 100parts by weight of polyamide. The pigments can be added to the reactorwith the starting materials or separately therefrom. The use of thetriacetonediamine compound (also as chain regulator constituent)distinctly improves the light stability of the polymer compared with apolymer comprising only pigment and containing no triacetonediamine.

This invention also relates to the use of inherently light- andheat-stabilized polyamide of this invention for producing filaments,fibers or films. This invention further relates to a process forproducing filaments based on polycaprolactam by high-speed spinning attakeoff speeds of at least 4000 m/min and to the filaments thusobtained. In addition, this invention encompasses the use of filamentsobtained according to this invention for producing fibers and fabricsand also the fibers and fabrics obtainable by this use.

The Examples which follow illustrate the invention.

General remarks concerning the Examples

The relative viscosity of the polyamides (pellets and filaments) wasdetermined in 1% strength solution (1 g/100 ml) in concentrated sulfuricacid (96% by weight) at 25° C. The end group content was determined byacidimetric titration. The amino end groups were titrated withperchloroacetic acid in a solution in 70:30 (parts by weight)phenol/methanol. The carboxyl end groups were titrated with potassiumhydroxide solution in a solution in benzyl alcohol.

The level in the polyamides of the triacetonediamine compound and of anydicarboxylic acids can be determined by hydrolyzing a sample in dilutemineral acid and analyzing the hydrolyzate by customary methods, forexample by gas chromatography.

The heat stability of the polyamide filaments was determined underconditions which substantially correspond to those of heat settingprocesses in subsequent treatment stages, for example heat setting ofBCF (bulked continuous filament) or tenter setting of textile fabrics. 5g hanks of the drawn filaments were rapidly introduced on a holdertogether with the comparative samples into a through-circulation ovenpreheated to 185° C. and left therein for 120 seconds from reattainmentof the air temperature measured in direct sample vicinity. The samplewas then immediately removed and cooled down in air at 20° C. roomtemperature. Filaments to be compared were treated together.

The damage incurred (compared with an untreated sample of the samefilament) was determined through the decrease in the relative viscosityand the amino group content and the increase in the carboxyl groupcontent.

The absolute decrease in the basic groups is then converted into apercentage decrease, based on the untreated yarn sample, to arrive at amore useful figure for actual service.

The ultimate extension was determined using an Uster Tensorapid I and aclamped length of 200 mm in the case of partially oriented yarn (POY)filaments, of 500 mm in the case of drawn and textured filaments. Thefilament time-to-rupture was within the range 20±2 seconds. Thepretensioning force was 0.025 cN/dtex in the case of POY and 0.05cN/dtex in the case of drawn filaments.

The tenacity R_(H) was calculated according to the following equation:

R_(H)=F_(H)/Tt_(V)

where F_(H) is the ultimate tensile strength [cN] and Tt_(V) is theoriginal linear density [dtex]. The ultimate tensile strength value usedwas the largest value obtained in the ultimate extension measurements.

The ultimate extension E_(H) was determined as the ratio of the lengthchange Δl at the moment of attainment of the ultimate tensile strengthto the original length l_(V) of the sample according to the followingequation:

E_(H)=Δl·100%/l_(V)

where Δl is the difference in the length of the sample at the time ofapplication of the ultimate tensile strength, l_(H), and the originallength l_(V).

REPRESENTATIVE EXAMPLE 1

The polymerization reactor used was a VK tube vertical column reactor asdescribed in EP 20946 composed of stainless steel, material No. 1,4541.The VK tube had an operating capacity of 340 l and was heated with aheat transfer oil.

A mixture of 100 parts by weight of molten caprolactam, 0.5 part byweight of water and 0.33 part by weight of terephthalic acid wascontinuously introduced into the first reaction zone at the top of theVK tube at a rate of 41 kg/h with stirring. At the same time,triacetone-diamine was continuously fed as a separate stream into thefirst reaction zone of the VK tube at a rate of 55 ml/h. Theconcentration of triacetonediamine was accordingly 0.087 mol %, and thatof terephthalic acid 0.23 mol %, each based on 1 mol of caprolactam. Thetemperature of the first reaction zone was 266° C.; the pressure in thevapor phase above the first reaction zone was 1.5 bar absolute. Thepolycaprolactam was discharged from the VK tube at the base thereof,converted into pellets, extracted with hot water and dried. The driedpolymer had a relative viscosity of 2.70, an amino end group content of39 meq/kg and a carboxyl end group content of 65 meq/kg.

The product was spun at high speed as godet POY from jets having a holediameter of 0.2 mm and a capillary length of 0.6 mm on an Ems-Inventapilot spinning plant at a melt temperature of 275° C. and a rate of 23g/min per jet.

The speeds were 4520 m/min for the 1st duo, 4530 m/min for the 2nd duoand 4500 m/min for the Barmag Craft winder.

Below the jet the filaments were cooled in a Barmag transverse flowquench box using a 20° C./65% relative humidity airstream having avelocity of 0.4 m/sec. The filaments were spin finished with acommercial spin finish composition (Limanol E 100, from Schill &Seilacher, 0.65% add-on filament) in the quench box via a metering pumpand ceramic oilers. The POY had the following properties: ultimateextension 72%, tenacity 4.1 cN/dtex, Uster standard test U %=0.6

The filaments were then cold-drawn at 820 m/min on a Zinser 14 Sdraw-twist machine to a draw ratio of 1:1.363. The filaments thusobtained had an ultimate extension of 37%, a tenacity of 5.2 cN/dtex andan Uster uniformity U % (standard test) of 0.7. The 12 filament yarnshad a linear density of 43.1 dtex.

The relative viscosity was 2.70, the amino end group concentration was35 and the carboxyl end group concentration was 63 meq/kg.

Comparative Example 1

Commercial nylon 6 of relative viscosity 2.67 without triacetonediaminewas spun under identical conditions as in Representative Example 1. ThePOY had the following properties: ultimate extension 73%, tenacity 4.0cN/dtex, Uster standard test U %=0.6.

The yarn was then cold-drawn to a draw ratio of 1:1.336. The yarns thusobtained had an ultimate extension of 43%, a tenacity of 4.8 cN/dtex andan Uster uniformity U % (standard test) of 0.5. The linear density ofthe 12 filament yarns was 43.8 dtex. The relative viscosity was 2.66,the amino end group content was 32 meq/kg, and the carboxyl end groupcontent was 53 meq/kg.

The yarns were subjected to a 120 s heat treatment in hot air at 185° C.and showed the following values:

TABLE 1 Representative Comparative Example 1 Example 1 Relativeviscosity untreated 2.70 2.66 treated 2.45 2.20 decrease −0.25 −0.46Amino end groups untreated 35 32 (meq/kg) treated 26 21 decrease −9 −11decrease (%) −26% −34% Carboxyl end untreated 63 53 groups treated 67 71(meq/kg) increase +4 +18

Table 1 reveals that the nylons 6 of this invention decrease less inrelative viscosity and amino group content and increase less in carboxylgroup content in the heat treatment than the polyamide of ComparativeExample 1 and thus possess better heat stabilization.

Representative Example 2

Caprolactam was polymerized in the same VK tube as in RepresentativeExample 1 in the presence of 0.38 mol % of terephthalic acid, 0.20 mol %of triacetonediamine, 0.5% by weight of water and 0.3% by weight oftitanium dioxide (as delusterant). The polymerization was carried out inthe first reaction zone at a temperature of 255° C. and at atmosphericpressure with a throughput of 25 kg/h. The procedure was otherwise incorrespondence with that described in Representative Example 1. Thedried product had a relative viscosity of 2.37, an amino end groupcontent of 45 meq/kg and a carboxyl end group content of 79 meq/kg.

The product was melted in a Barmag single-screw extruder and fed at amelt temperature of 270° C. into a Barmag SP 42 spinning system. Themelt was spun at a rate of 22.6 g/min per jet through 12-hole spinningjets having capillary holes 0.20 mm in diameter and 0.60 mm in length toproduce 12 filament strands having an as-spun (POY) linear density of 52dtex and taken up at 4500 m/min. After passing through a quench box witha transverse quench flow of 0.40 m/sec and spin finishing with from 0.60to 0.65% of a commercial spin finish composition (Limanol E 100 fromSchill & Seilacher as 8% strength solution) the filament strands weretaken off via 2 godet duos at 4510 m/min and 4535 m/min, respectively.The winding head used was an axially driven Barmag Craft winder. The POYhad an ultimate extension of 65%, a tenacity of 4.6 cN/dtex and aboil-off shrinkage of 9%.

The POY was cold-drawtwisted at 748 m/min on a Rieter J5/10a draw-twistmachine. The yarn tension in the prestretch zone was 0.8%, and the totaldraw ratio was 1:1.298.

The drawn filament yarns had an ultimate extension of 36%, a tenacity of5.2 cN/dtex, a linear density of 44 dtex for 12 filaments and an Uster U% (standard test) of 0.7.

The relative viscosity was found to be 2.41, the amino end group contentwas found to be 42 meq/kg and the carboxyl end group content was foundto be 74 meq/kg.

Comparative Example 2

Commercial nylon 6 having a relative viscosity of 2.39 and containing notriacetonediamine was extruded in the manner described in RepresentativeExample 2. Cooling and spin finishing of the filaments were carried outas described above. The POY was wound up at 4500 m/min without godets.The POY had an ultimate extension of 62%, a tenacity of 4.2 cN/dtex anda boil-off shrinkage of 9%.

The POY was cold-drawn as in Representative Example 2 to a total drawratio of 1:1.279. The drawn filament yarns had an ultimate extension of34%, a tenacity of 4.6 cN/dtex, a linear density of 43.6 dtex for 12filaments and an Uster value U % (standard test) of 0.9.

The relative viscosity of the yarns was 2.41, the amino end groupcontent was 25 meq/kg and the carboxyl end group content was 65 meq/kg.

The yarns were subjected to conditions corresponding to a textile tentersetting (185° C. hot air, 120 sec) and the following properties weremeasured:

TABLE 2 Representative Comparative Example 2 Example 2 Relativeviscosity untreated 2.41 2.41 treated 2.28 1.84 decreased −0.13 −0.57Amino end groups untreated 42 25 (meq/kg) treated 34 13 decrease −8 −12decrease (%) −19% −48% Carboxyl end untreated 74 65 groups treated 75 93(meq/kg) increase +1 +28

Table 2 clearly shows that caprolactam polymerized to nylon 6 in thepresence of triacetonediamine has better heat stabilization than thenylon 6 of Comparative Example 2, which contains no triacetonediamine.

Representative Example 3

Polyamide prepared as in Representative Example 2 but without theaddition of titanium dioxide was subjected to high-speed spinning inaccordance with Representative Example 2. The POY had an ultimateextension of 64%, a tenacity of 4.7 cN/dtex and a boil-off shrinkage of10%.

The drawing was carried out under the conditions recited inRepresentative Example 2. Thereafter the drawn yarns had an ultimateextension of 37%, a tenacity of 5.4 cN/dtex, a boil-off shrinkage of14%, an Uster uniformity U % (standard test) of 0.8 and a 12-filamentlinear density of 44 dtex.

The relative viscosity was 2.40, the amino end group content was 42meq/kg, and the carboxyl end group content was 74 meq/kg.

Comparative Example 3A/3B

2 types of commercial nylon 6 of relative viscosity 2.40 (3A) and 2.44(3B), respectively, were subjected to high-speed spinning in accordancewith Representative Example 2. The spinning temperature was 275° C., andthe speed of the godet duos was 4510 m/min and 4520 m/min, respectively.

TABLE 3 The POY had the following properties: RepresentativeRepresentative Example 3A Example 3B Ultimate extension 64% 68% Tenacity4.4 cN/dtex 4.2 cN/dtex Boil-off shrinkage  8%  8% Uster (standard test)U% 0.6%  0.5%  12-filament linear density 51 dtex 52 dtex The POY wasthen cold-drawn on draw-twist machines to the draw ratios: 1:1.2571:1.313 and had the data. Ultimate extension 44% 38% Tenacity 5.0cN/dtex 4.8 cN/dtex Boil-off shrinkage 11% 12% Uster (standard test) U%0.6%  0.8%  12-filament linear density 45 dtex 43 dtex The followingdata were determined following thc hot-air treatment: Rep. Ex. Comp. Ex.Comp. Ex. 3 3A 3B Relative viscosity untreated 2.40 2.37 2.45 treated2.19 1.93 2.23 deceased −0.21 −0.44 −0.22 Amino end groups untreated 4224 43 (meq/kg) treated 34 16 27 decrease −8 −8 −16 decrease −19% −33%−37% (%) Carboxyl end untreated 74 65 51 groups treated 78 86 64(meq/kg) increase +4 +21 +13

According to Table 3, nylon 6 of this invention has better heatstabilization than the nylon 6 types of the comparative examples.

Representative Example 4

Caprolactam was polymerized in the same VK tube as in RepresentativeExample 1 in the presence of 0.55% by weight (0.375 mol %) ofterephthalic acid, 0.33% by weight (0.239 mol %) of triacetonediamine,0.5% by weight of water and 0.3% by weight of titanium dioxide. Thepolymerization was carried out in the first reaction zone at atemperature of 255° C. and at atmospheric pressure with a throughput of25 kg/h. The procedure was otherwise in correspondence with thatdescribed in Representative Example 1. The dried product had a relativeviscosity of 2.42, an amino end group content of 46 meq/kg and acarboxyl end group content of 70 meq/kg. The extractables content was0.38%.

This was followed by godetless spinning at 4500 m/min in accordance withComparative Example 2, then cold-drawing to a draw ratio of 1:1.229 andwarping at 600 m/min.

The POY had a 12 filament linear density of 52 dtex, an ultimateextension of 59% and a tenacity of 4.1 cN/dtex.

An average of 0.5 defects/100 km were found in the Elkometer test (gapsize 45 μm).

The drawn yarn has an ultimate extension of 36% and a tenacity of 4.3cN/dtex. The 12 filament linear density was 46 dtex.

Comparative Example 4

Caprolactam was polymerized in the same VK tube as in RepresentativeExample 4 in the presence of 0.53% by weight (0.361 mol %) ofterephthalic acid, 0.5% by weight of water and 0.3% by weight oftitanium dioxide. The polymerization was carried out in the firstreaction zone at a temperature of 252° C. The procedure was otherwise incorrespondence with that described in Representative Example 4. Thedried product had a relative viscosity of 2.39, an amino end groupcontent of 27 meq/kg and a carboxyl end group content of 92 meq/kg. Theextractables content was 0.32%.

50 kg of the above nylon 6 chips were admixed with 165 g oftriacetonediamine (TAD) (0.33% by weight) in liquid form by drumming onin a gyro wheel mixer for 2 hours.

The chips accordingly comprised the same amount of TAD in admixture andcontained virtually the same terephthalic acid content (as part of thepolymer) as the above-described product 4; the two products wereidentical except for the manner of the addition of the TAD.

The drummed-on TAD does not absorb completely into the chips. Theyremain TAD-moist and have a strong amine odor. This property isextremely disadvantageous in handling; in addition, extensive safetyprecautions are necessary, since TAD is corrosive.

During the residence time in the spinning system, the viscosityincreases normally in the case of Representative Example 4, whereas itdecreases dramatically in the case of Comparative Example 4. Otheradvantages of Representative Example 4 are the comparatively smallchange in the number of amino groups and in the extractables content(determination: 16 hours of extraction with methanol under reflux) andthe fact that there is significantly less fuming in the spinneret regionduring spinning.

TABLE 4 Chemical data of free-fall filaments Rep. Ex. 4 Comp. Ex. 4Relative viscosity 2.48 (+0.06)¹ 2.24 (−0.15)¹ End groups Amino (meg/kg)43 (−3) 54 (+27) Carboxyl (meg/kg) 67 (−3) 88 (−4) Extract (%) 1.4(+1.0) 1.8 (+1.5) ¹Values in brackets: change compared with chips used;in the case of Comparative Example 4, compared with the base polymerwithout TAD.

The spinning and further processing were carried out under theconditions recited in Representative Example 4. The POY had a 12filament linear density of 52 dtex, an ultimate extension of 54% and atenacity of 3.8 cN/dtex. An average of 7.5 defects (nodules, brokenfilaments, loops)/100 km were found in the Elkometer test.

After drawing, the ultimate extension was 35% and the tenacity 4.2cN/dtex.

TABLE 5 Rep. Ex. 4 Comp. Ex. 4 Broken filaments/ 1.2 4.0 100 kgElkometer test 0.5 7.5 defects/100 km Drawing defect/100 1.8 14.5 kgWarping defect/100 0.037 >0.65 km

As is discernible from Table 5, the nylon 6 of Representative Example 4according to the invention has lower defect numbers in all processingstages than the nylon 6 of Comparative Example 4, into which the TAD wasincorporated by mixing into the polyamide.

In Representative Example 4, TAD is more completely/strongly attached inthe polyamide than in Comparative Example 4. Thus, less amine passesinto the aqueous phase in extraction processes (in dyeings, forexample).

Following one hour extraction with boiling water under reflux of POYwound up without spin finish, the following chemical data weredetermined:

TABLE 6 Rep. Ex. 4 Comp. Ex. 4 Rel. viscosity before extraction 2.422.20 after extraction 2.49 2.26 difference +0.07 +0.06 Amino end beforeextraction 42 55 groups after extraction 42 50 (meg/kg) difference ±0 −5

As is evident from Table 6, the number of amino end groups before andafter extraction remains the same in the polyamide of this invention,whereas the comparative example has fewer amino end groups afterextraction. Thus, less amine passes into the aqueous phase on extractionof the polyamide of this invention.

Comparative Example 5

Commercial nylon 6 of relative viscosity 2.39, delustered with 0.3%titanium dioxide and containing no triacetonediamine was spun intofilaments in the manner described in Comparative Example 2.

The POY had a 12 filament linear density of 51 dtex, an ultimateextension of 57% and a tenacity of 3.8 cN/dtex. After cold drawing to adraw ratio of 1:1.244, the values listed below in Table 7 for theuntreated sample were determined.

The irradiation and the measurement of the ultimate extension andultimate tensile strength were carried out jointly with RepresentativeExample 5. The results are listed in Table 7.

Representative Example 5

Caprolactam was polymerized from the same starting materials andquantities under the conditions specified in Representative Example 4using the same titanium dioxide type as in Comparative Example 5. Thedried polyamide had a relative viscosity of 2.43, an amino end groupcontent of 44 meq/kg and a carboxyl end group content of 71 meq/kg. Theextractables content was 0.36%.

Spinning was carried out godetlessly at 4500 m/min as described inComparative Example 2. The POY had a 12 filament linear density of 51dtex, an ultimate extension of 61% and a tenacity of 4.3 cN/dtex.

After cold drawing to a draw ratio of 1:1.244, the values listed belowin Table 7 for the untreated sample were determined.

The yarns were then wound on frames and irradiated for 28 days in aXenotest 450 from Heraeus, Hanau, and the residual ultimate extensionand the residual ultimate tensile strength were determined in accordancewith DIN 53834 using a clamped length of 100 mm on a Zwick UPM 1425tensile tester. The results are listed in Table 7.

TABLE 7 Rep. Ex. 5 Comp. Ex. 5 Untreated yarns 12-filament lineardensity (dtex) 44 44 Ultimate extension (%) 35 39 Ultimate tensilestrength (cN) 199 196 Tenacity 4.52 4.45 (cN/dtex) After 28 days′irradiation in Xenotest 450 23 16 Residual ultimate extension (%) (66)(41) (= % of original value) (%) 136 97 Residual ultimate tensile (cN)strength (68) (49) (= % of original value) (%)

It is clear from Table 7 that the polyamide prepared in the presence oftriacetonediamine and TiO₂ (Representative Example 5) has a distinctlyimproved light stability compared with a comparative polymer(Comparative Example 5) including only TiO₂ and no triacetonediamine.

We claim:
 1. A process for preparing polyamides which comprises:polymerizing caprolactam, or polymerizing at least one dicarboxylic acidselected from adipic acid, sebacic acid and terephthalic acid and atleast one diamine selected from hexamethylenediamine andtetra-methylenediamine, or polymerizing dicarboxylic acid-diamine saltsof said dicarboxylic acids and said diamines in the presence of at leastone triacetonediamine compound of the formula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,which process is carried out in the presence of at least one pigment. 2.A process for preparing polyamides which comprises: polymerizingcaprolactam, or polymerizing at least one dicarboxylic acid selectedfrom adipic acid, sebacic acid and terephthalic acid and at least onediamine selected from hexamethylenediamine and tetra-methylenediamine,or polymerizing dicarboxylic acid-diamine salts of said dicarboxylicacids and said diamines in the presence of at least onetriacetonediamine compound of the formula

where R is benzyl.
 3. A process for preparing polyamides whichcomprises: polymerizing caprolactam, or polymerizing at least onedicarboxylic acid selected from adipic acid, sebacic acid andterephthalic acid and at least one diamine selected fromhexamethylenediamine and tetra-methylenediamine, or polymerizingdicarboxylic acid-diamine salts of said dicarboxylic acids and saiddiamines in the presence of at least one triacetonediamine compound ofthe formula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,which process is carried out in the presence of at least one chainreactor.
 4. An inherently light- and heat-stabilized polyamidecontaining an amine radical of the formula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,chemically bonded to a terminal carboxyl group of the polymer chain,where the chemical bond is established prior to or during the formationof the polyamide, and further containing at least one pigment, andwherein said polyamide is specifically adapted for the manufacture offibers and filaments.
 5. An inherently light- and heat-stabilizedpolyamide containing from 0.03 to 0.8 mol-%, based on 1 mol ofcarboxamide groups of the polymer chain of the polyamide, of an amineradical of the formula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,chemically bonded to a terminal carboxyl group of the polymer chain,where the chemical bond is established prior to or during the formationof the polyamide, and wherein said polyamide is specifically adapted forthe manufacture of fibers and filaments.
 6. The polyamide defined inclaim 5, containing from 0.06 to 0.4 mol-%, based on 1 mol ofcarboxamide groups of the polymer chain of the polyamide, of the amineradical.
 7. An inherently light- and heat-stabilized polyamidecontaining an amine radical of the formula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,chemically bonded to a terminal carboxyl group of the polymer chain,where the chemical bond is established prior to or during the formationof the polyamide, prepared by polymerization in the presence of at leastone chain regulator, and wherein said polyamide is specifically adaptedfor the manufacture of fibers and filaments.
 8. An inherently light- andheat-stabilized polyamide containing an amine radical of the formula

where R is benzyl, chemically bonded to a terminal carboxyl group of thepolymer chain, where the chemical bond is established prior to or duringthe formation of the polyamide, and wherein said polyamide isspecifically adapted for the manufacture of fibers and filaments.
 9. Aninherently stabilized polyamide containing an amine radical of theformula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,chemically bonded to a terminal carboxyl group of the polymer chain,where the chemical bond is established prior to or during the formationof the polyamide, and further containing at least one pigment, andwherein said polyamide is specifically adapted for the manufacture offibers and filaments.
 10. An inherently stabilized polyamide containingfrom 0.03 to 0.8 mol-%, based on 1 mol of carboxamide groups of thepolymer chain of the polyamide, of an amine radical of the formula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,chemically bonded to a terminal carboxyl group of the polymer chain,where the chemical bond is established prior to or during the formationof the polyamide, and wherein said polyamide is specifically adapted forthe manufacture of fibers and filaments.
 11. The polyamide defined inclaim 10, containing from 0.06 to 0.4 mol-%, based on 1 mol ofcarboxamide groups of the polymer chain of the polyamide, of the amineradical.
 12. An inherently stabilized polyamide containing an amineradical of the formula

where R is hydrogen or hydrocarbyl having from 1 to 20 carbon atoms,chemically bonded to a terminal carboxyl group of the polymer chain,where the chemical bond is established prior to or during the formationof the polyamide, prepared by polymerization in the presence of at leastone chain regulator, and wherein said polyamide is specifically adaptedfor the manufacture of fibers and filaments.
 13. An inherentlystabilized polyamide containing an amine radical of the formula

where R is benzyl, chemically bonded to a terminal carboxyl group of thepolymer chain, where the chemical bond is established prior to or duringthe formation of the polyamide, and wherein said polyamide isspecifically adapted for the manufacture of fibers and filaments.
 14. Afilament or fiber comprising the polyamide defined in claim
 4. 15. Afabric comprising the filament or fiber defined in claim
 14. 16. Afilament or fiber comprising the polyamide defined in claim
 5. 17. Afabric comprising the filament or fiber defined in claim
 16. 18. Afilament or fiber comprising the polyamide defined in claim
 7. 19. Afabric comprising the filament or fiber defined in claim
 18. 20. Afilament or fiber comprising the polyamide defined in claim
 8. 21. Afabric comprising the filament or fiber defined in claim
 19. 22. Afilament or fiber comprising the polyamide defined in claim
 9. 23. Afabric comprising the filament or fiber defined in claim
 22. 24. Afilament or fiber comprising the polyamide defined in claim
 10. 25. Afabric comprising the filament or fiber defined in claim
 24. 26. Afilament or fiber comprising the polyamide defined in claim
 12. 27. Afabric comprising the filament or fiber defined in claim
 26. 28. Afilament or fiber comprising the polyamide defined in claim
 13. 29. Afabric comprising the filament or fiber defined in claim 28.